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  Subjects -> ENGINEERING (Total: 1961 journals)
    - CHEMICAL ENGINEERING (153 journals)
    - CIVIL ENGINEERING (149 journals)
    - ELECTRICAL ENGINEERING (81 journals)
    - ENGINEERING (1114 journals)
    - ENGINEERING MECHANICS AND MATERIALS (292 journals)
    - HYDRAULIC ENGINEERING (46 journals)
    - INDUSTRIAL ENGINEERING (52 journals)
    - MECHANICAL ENGINEERING (74 journals)

CHEMICAL ENGINEERING (153 journals)                  1 2     

ACS Combinatorial Science     Full-text available via subscription   (Followers: 9)
Acta Crystallographica Section B: Structural Science, Crystal Engineering and Materials     Hybrid Journal   (Followers: 4)
Acta Polymerica     Hybrid Journal   (Followers: 6)
Additives for Polymers     Full-text available via subscription   (Followers: 19)
Adhesion Adhesives & Sealants     Hybrid Journal   (Followers: 4)
Advanced Chemical Engineering Research     Open Access   (Followers: 8)
Advanced Powder Technology     Hybrid Journal   (Followers: 13)
Advances in Chemical Engineering     Full-text available via subscription   (Followers: 16)
Advances in Chemical Engineering and Science     Open Access   (Followers: 21)
Advances in Polymer Technology     Hybrid Journal   (Followers: 11)
African Journal of Pure and Applied Chemistry     Open Access   (Followers: 4)
Annual Review of Analytical Chemistry     Full-text available via subscription   (Followers: 9)
Annual Review of Chemical and Biomolecular Engineering     Full-text available via subscription   (Followers: 10)
Anti-Corrosion Methods and Materials     Hybrid Journal   (Followers: 4)
Applied Petrochemical Research     Open Access   (Followers: 3)
Asia-Pacific Journal of Chemical Engineering     Hybrid Journal   (Followers: 6)
Biochemical Engineering Journal     Hybrid Journal   (Followers: 8)
Biomass Conversion and Biorefinery     Partially Free   (Followers: 5)
BMC Chemical Biology     Open Access   (Followers: 4)
Brazilian Journal of Chemical Engineering     Open Access   (Followers: 2)
Bulletin of the Chemical Society of Ethiopia     Open Access   (Followers: 1)
Carbohydrate Polymers     Hybrid Journal   (Followers: 8)
Catalysts     Open Access   (Followers: 6)
Chemical and Petroleum Engineering     Hybrid Journal   (Followers: 7)
Chemical and Process Engineering     Open Access   (Followers: 3)
Chemical and Process Engineering Research     Open Access   (Followers: 5)
Chemical Communications     Full-text available via subscription   (Followers: 29)
Chemical Engineering & Technology     Hybrid Journal   (Followers: 24)
Chemical Engineering and Processing: Process Intensification     Hybrid Journal   (Followers: 10)
Chemical Engineering and Science     Open Access   (Followers: 2)
Chemical Engineering Communications     Hybrid Journal   (Followers: 10)
Chemical Engineering Journal     Hybrid Journal   (Followers: 18)
Chemical Engineering Research and Design     Hybrid Journal   (Followers: 15)
Chemical Engineering Science     Hybrid Journal   (Followers: 10)
Chemical Geology     Hybrid Journal   (Followers: 9)
Chemical Papers     Hybrid Journal   (Followers: 3)
Chemical Product and Process Modeling     Full-text available via subscription   (Followers: 3)
Chemical Reviews     Full-text available via subscription   (Followers: 292)
Chemical Society Reviews     Full-text available via subscription   (Followers: 28)
Chemical Technology     Open Access   (Followers: 4)
ChemInform     Hybrid Journal   (Followers: 3)
Chemistry & Industry     Hybrid Journal   (Followers: 2)
Chemistry Central Journal     Open Access   (Followers: 5)
Chemistry of Materials     Full-text available via subscription   (Followers: 196)
Chemometrics and Intelligent Laboratory Systems     Hybrid Journal   (Followers: 6)
ChemSusChem     Hybrid Journal   (Followers: 7)
Chinese Chemical Letters     Full-text available via subscription   (Followers: 1)
Chinese Journal of Chemical Engineering     Full-text available via subscription   (Followers: 3)
Chinese Journal of Chemical Physics     Hybrid Journal   (Followers: 1)
Coke and Chemistry     Hybrid Journal  
Coloration Technology     Hybrid Journal   (Followers: 1)
Computational Biology and Chemistry     Hybrid Journal   (Followers: 8)
Computer Aided Chemical Engineering     Full-text available via subscription   (Followers: 2)
Computers & Chemical Engineering     Hybrid Journal   (Followers: 6)
Corrosion Reviews     Full-text available via subscription   (Followers: 4)
Crystal Research and Technology     Hybrid Journal   (Followers: 2)
Current Opinion in Chemical Engineering     Open Access   (Followers: 3)
Education for Chemical Engineers     Hybrid Journal   (Followers: 4)
European Polymer Journal     Hybrid Journal   (Followers: 41)
Fibers and Polymers     Full-text available via subscription   (Followers: 3)
Focusing on Modern Food Industry     Open Access   (Followers: 3)
Frontiers of Chemical Science and Engineering     Hybrid Journal   (Followers: 1)
Geochemistry International     Hybrid Journal  
Handbook of Powder Technology     Full-text available via subscription   (Followers: 2)
High Performance Polymers     Hybrid Journal  
Indian Chemical Engineer     Hybrid Journal   (Followers: 3)
Indian Journal of Chemical Technology (IJCT)     Open Access   (Followers: 12)
Industrial & Engineering Chemistry     Full-text available via subscription   (Followers: 9)
Industrial & Engineering Chemistry Research     Full-text available via subscription   (Followers: 17)
Industrial Chemistry Library     Full-text available via subscription   (Followers: 4)
International Journal of Chemical and Petroleum Sciences     Open Access   (Followers: 1)
International Journal of Chemical Engineering     Open Access   (Followers: 6)
International Journal of Chemical Reactor Engineering     Full-text available via subscription   (Followers: 3)
International Journal of Chemical Technology     Open Access   (Followers: 3)
International Journal of Chemoinformatics and Chemical Engineering     Full-text available via subscription   (Followers: 2)
International Journal of Food Science     Open Access   (Followers: 2)
International Journal of Industrial Chemistry     Open Access  
International Journal of Polymeric Materials     Hybrid Journal   (Followers: 3)
International Journal of Science and Engineering     Open Access   (Followers: 7)
International Journal of Waste Resources     Open Access   (Followers: 5)
ISRN Chemical Engineering     Open Access   (Followers: 4)
ISRN Polymer Science     Open Access   (Followers: 11)
Journal of Applied Crystallography     Hybrid Journal   (Followers: 4)
Journal of Applied Electrochemistry     Hybrid Journal   (Followers: 7)
Journal of Applied Polymer Science     Hybrid Journal   (Followers: 186)
Journal of Biomaterials Science, Polymer Edition     Hybrid Journal   (Followers: 8)
Journal of Chemical & Engineering Data     Full-text available via subscription   (Followers: 6)
Journal of Chemical Ecology     Hybrid Journal   (Followers: 2)
Journal of Chemical Engineering     Open Access   (Followers: 4)
Journal of Chemical Engineering and Materials Science     Open Access  
Journal of Chemical Science and Technology     Open Access   (Followers: 1)
Journal of Chemical Sciences     Partially Free   (Followers: 15)
Journal of Chemical Technology & Biotechnology     Hybrid Journal   (Followers: 2)
Journal of Chemical Theory and Computation     Full-text available via subscription   (Followers: 9)
Journal of Coatings     Open Access   (Followers: 2)
Journal of Crystallization Process and Technology     Open Access   (Followers: 5)
Journal of Food Measurement and Characterization     Hybrid Journal  
Journal of Fuel Chemistry and Technology     Full-text available via subscription   (Followers: 5)
Journal of Fuels     Open Access  
Journal of Geochemical Exploration     Hybrid Journal  

        1 2     

Journal Cover Chemical Engineering Science
   Journal TOC RSS feeds Export to Zotero [12 followers]  Follow    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
     ISSN (Print) 0009-2509
     Published by Elsevier Homepage  [2570 journals]   [SJR: 1.033]   [H-I: 103]
  • Effect of liquid fraction and bubble size distribution on the polarised
           light scattering characteristics of Casein foam
    • Abstract: Publication date: 27 January 2015
      Source:Chemical Engineering Science, Volume 122
      Author(s): Shaoyu Qian , John J.J. Chen
      A polarised light scattering experimental set-up was designed to conduct experiments using Casein foams with monodispersed and bidispersed bubble size distributions. Foams were initially generated under forced drainage conditions to maintain a uniform axial liquid fraction profile. Subsequently, the foams entered a free drainage period. During this period, the liquid fraction, the bubble size distribution and the polarisation parameters of scattered light due to the foam were measured individually. It was found that both the liquid fraction and the bubble size distribution of Casein foams varied simultaneously with drainage time. Therefore, multiple regression analysis was performed to investigate the individual effect of these two foam factors on the polarisation state. Four of the polarisation parameters (degree of polarisation, degree of linear polarisation, degree of circular polarisation, ellipticity angle) were shown to be associated with the liquid fraction and/or the bubble size distribution to different extents. However, the remaining parameter, orientation angle, was completely independent of the liquid fraction and the bubble size distribution. These results can be used for the development of the polarised light scattering method in the study of protein foams.


      PubDate: 2014-10-17T09:48:10Z
       
  • CFD–DEM simulation of biomass gasification with steam in a fluidized
           bed reactor
    • Abstract: Publication date: 27 January 2015
      Source:Chemical Engineering Science, Volume 122
      Author(s): Xiaoke Ku , Tian Li , Terese Løvås
      A comprehensive CFD–DEM numerical model has been developed to simulate the biomass gasification process in a fluidized bed reactor. The methodology is based on an Eulerian–Lagrangian concept, which uses an Eulerian method for gas phase and a discrete element method (DEM) for particle phase. Each particle is individually tracked and associated with multiple physical (size, density, composition, and temperature) and thermo-chemical (reactive or inert) properties. Particle collisions, hydrodynamics of dense gas-particle flow in fluidized beds, turbulence, heat and mass transfer, radiation, particle shrinkage, pyrolysis, and homogeneous and heterogeneous chemical reactions are all considered during biomass gasification with steam. A sensitivity analysis is performed to test the integrated model׳s response to variations in three different operating parameters (reactor temperature, steam/biomass mass ratio, and biomass injection position). Simulation results are analyzed both qualitatively and quantitatively in terms of particle flow pattern, particle mixing and entrainment, bed pressure drop, product gas composition, and carbon conversion. Results show that higher temperatures are favorable for the products in endothermic reactions (e.g. H2 and CO). With the increase of steam/biomass mass ratio, H2 and CO2 concentrations increase while CO concentration decreases. The carbon conversion decreases as the height of injection point increases owing to both an increase of solid entrainment and a decrease of particle residence time and particle temperature. Meanwhile, the calculated results compare well with the experimental data available in the literature. This indicates that the proposed CFD–DEM model and simulations are successful and it can play an important role in the multi-scale modeling of biomass gasification or combustion in fluidized bed reactor.


      PubDate: 2014-10-17T09:48:10Z
       
  • Mercury capture by a regenerable sorbent under oxycoal combustion
           conditions: Effect of SO2 and O2 on capture efficiency
    • Abstract: Publication date: 27 January 2015
      Source:Chemical Engineering Science, Volume 122
      Author(s): C. Gómez-Giménez , D. Ballestero , R. Juan , B. Rubio , M.T. Izquierdo
      The present study evaluates an Au/C sorbent based on the direct reduction of a gold salt on a carbon coated structured cordierite monolith for mercury capture under oxyfiring conditions. Both mercury retention efficiency and mercury retention capacity were tested in a bench scale plant under different conditions. The influence of gas temperature (50–150°C) and gas composition (CO2, N2, SO2, and O2) on sorbent performance for mercury capture is evaluated and discussed. The amount of mercury captured did not vary significantly with temperature under a CO2 atmosphere. These results were compared with those obtained under N2 atmosphere with no remarkable differences found between them. High retention efficiencies were obtained despite the small amount of gold used. The presence of SO2 and O2 in the flue gas led to mercury oxidation that seemed to be mainly promoted by SO2 under the presence of the Au-sorbent.


      PubDate: 2014-10-11T21:16:55Z
       
  • High-temperature pressure swing adsorption cycle design for
           sorption-enhanced water–gas shift
    • Abstract: Publication date: 27 January 2015
      Source:Chemical Engineering Science, Volume 122
      Author(s): Jurriaan Boon , P.D. Cobden , H.A.J. van Dijk , M. van Sint Annaland
      Sorption-enhanced water–gas shift (SEWGS) combines the water–gas shift reaction with in situ adsorption of CO2 on potassium-promoted hydrotalcite (K-HTC) and thereby allows production of hot, high pressure H2 from syngas in a single unit operation. SEWGS is a cyclic process, that comprises high pressure adsorption and rinse, pressure equalisation, and low pressure purge. Here, results are presented of a SEWGS cycle design study, based on recently developed expressions for the interaction of CO2 and H2O with K-HTC. It is shown that during the cycle, steam adsorbs in the rinse step and desorbs during the subsequent reduction in pressure, thereby improving the CO2 purity in the column and thus enhancing the efficiency of the rinse. A parameter study based on numerical simulations shows that the carbon capture ratio depends mainly on the purge steam to carbon feed ratio, whereas the CO2 product purity depends mainly on the rinse steam to carbon feed ratio. An optimisation yields a SEWGS cycle that consumes significantly less steam than cycle designs previously reported in the literature.
      Graphical abstract image Highlights

      PubDate: 2014-10-11T21:16:55Z
       
  • An integrative image measurement technique for dense bubbly flows with a
           wide size distribution
    • Abstract: Publication date: 27 January 2015
      Source:Chemical Engineering Science, Volume 122
      Author(s): Ashish Karn , Christopher Ellis , Roger Arndt , Jiarong Hong
      The measurements of bubble size distribution are ubiquitous in many industrial applications in chemical engineering. The conventional methods using image analysis to measure bubble size are limited in their robustness and applicability in highly turbulent bubbly flows. These flows usually impose significant challenges for image processing such as a wide range of bubble size distribution, spatial and temporal inhomogeneity of image background including in-focus and out-of-focus bubbles, as well as the excessive presence of bubble clusters. This article introduces a multi-level image analysis approach to detect a wide size range of bubbles and resolve bubble clusters from images obtained in a turbulent bubbly wake of a ventilated hydrofoil. The proposed approach was implemented to derive bubble size and air ventilation rate from the synthetic images and the experiments, respectively. The results show a great promise in its applicability for online monitoring of bubbly flows in a number of industrial applications.


      PubDate: 2014-10-11T21:16:55Z
       
  • Detailed numerical simulations of catalytic fixed-bed reactors:
           Heterogeneous dry reforming of methane
    • Abstract: Publication date: 27 January 2015
      Source:Chemical Engineering Science, Volume 122
      Author(s): Gregor D. Wehinger , Thomas Eppinger , Matthias Kraume
      Highly endothermic (or exothermic) heterogeneous catalytic reactions are performed commonly in fixed-bed reactors with small tube-to-particle-diameter ratios N both in industrial and lab-scale applications. For these reactor configurations conventional plug flow models and pseudo-homogeneous kinetic models fail. An adequate modeling can be carried out with full computational fluid dynamics (CFD) in combination with detailed reaction mechanisms. In this study, a full three-dimensional fixed-bed reactor for the catalytic dry reforming of methane (DRM) over rhodium was simulated with a detailed reaction mechanism. The bed consists of 113 spherical solid particles in which thermal conductivity was considered. Two different Reynolds numbers were investigated, i.e., 35 and 700. The simulated DRM fixed-bed reactor demonstrates the strong interaction between chemical kinetics and transport of momentum, heat and mass. The observed velocity, temperature and species fields are characterized by their three-dimensional behavior and interactions highlighting their complexity and discrepancy from lumped model predictions. In addition, the reaction mechanism determines regions with catalyst deactivation by carbon deposition. This study demonstrates the advantages of modeling heterogeneous catalytic fixed-bed reactors with small N fully in three-dimensional in combination with detailed reaction mechanisms. Finally, this modeling approach reduces dependencies on empiricism for the calculation of multiscale reaction devices.


      PubDate: 2014-10-11T21:16:55Z
       
  • A comparison of magnetic resonance, X-ray and positron emission particle
           tracking measurements of a single jet of gas entering a bed of particles
    • Abstract: Publication date: 27 January 2015
      Source:Chemical Engineering Science, Volume 122
      Author(s): M. Pore , G.H. Ong , C.M. Boyce , M. Materazzi , J. Gargiuli , T. Leadbeater , A.J. Sederman , J.S. Dennis , D.J. Holland , A. Ingram , P. Lettieri , D.J. Parker
      Measurements of the lengths of a single jet of gas entering a packed bed were made using magnetic resonance imaging (MRI), positron emission particle tracking (PEPT) and X-ray radiography and the results compared. The experiments were performed using a Perspex bed (50mm i.d.) of poppy seeds: air at 298K was admitted to the base of the bed through a single, central orifice, 2mm in diameter. Poppy seeds (Geldart Group B, measured minimum fluidisation velocity with air at 298K and 1atm of 0.13m/s and particle density ~1060kg/m3) were used because of their high content of oil, which contains mobile protons and hence is suitable for MRI examination. The lengths of jet measured using the three techniques were in agreement between 50m/s<U o <100m/s, where U o is the superficial velocity through the orifice. Below U o =50m/s, X-ray measurements of jet lengths were shorter than those measured using MRI. This was attributed to the minimum diameter of void, found to be 5mm, detectable in a 50mm bed using ultra-fast X-ray measurements. PEPT is most commonly used to calculate particle velocities, whilst jet lengths are usually calculated from determinations of voidage. However, the particle locations determined in this work by PEPT were used to calculate a fractional occupancy count, from which a jet length could be inferred.


      PubDate: 2014-10-11T21:16:55Z
       
  • Dissipative particle dynamics study of the water/benzene/caprolactam
           system in the absence or presence of non-ionic surfactants
    • Abstract: Publication date: 27 January 2015
      Source:Chemical Engineering Science, Volume 122
      Author(s): Kaihang Shi , Cheng Lian , Zhishan Bai , Shuangliang Zhao , Honglai Liu
      A dissipative particle dynamics (DPD) simulation is performed to study the properties of water/benzene/caprolactam (W/B/CPL) system in the absence or presence of different non-ionic surfactants. The interaction parameters involved in the constructed coarse-grained model are determined by combining two solubility-parameter models and all-atom molecular dynamics. By using the DPD method, we first show that the interfacial tensions in the W/B/CPL system can be quantitatively predicted and compared with available experimental and other theoretical data. Secondly, by calculating the density profile of CPL and the efficiency of the surfactant at various conditions, we demonstrate that (i) unlike Traube׳s rule, the efficiency of the surfactant does not always improve with an increase in its hydrophobic tail length, and due to the accumulation of CPL at the interface, this tail length effect becomes nearly negligible when the tail is long; (ii) CPL, like a weak surfactant, is capable of activating surfactants at the interface by improving the efficiency of surfactant; and (iii) the addition of surfactants (especially with short tail lengths) into the W/B/CPL system can drive CPL into the water-rich phase, which can be applied to the design of more efficient industrial extraction process for recycling CPL.


      PubDate: 2014-10-11T21:16:55Z
       
  • Heat transfer in turbulent bubbly flow in vertical channels
    • Abstract: Publication date: 27 January 2015
      Source:Chemical Engineering Science, Volume 122
      Author(s): Sadegh Dabiri , Gretar Tryggvason
      This paper examines the convective heat transfer in the turbulent bubbly flow between two parallel walls under a constant heat flux condition with a Reynolds number of up to Re=5600 based on the channel width and the average velocity. Direct numerical simulation is used to fully resolve the turbulent flow and the motion of bubbles. The channel is vertical and the flow is directed upward so that nearly spherical bubbles accumulate at the wall but deformable bubbles remain in the middle. The results show that the presence of bubbles enhances the mixing and consequently the heat transfer for both nearly spherical and deformable bubbles, as compared with results for single-phase flows.


      PubDate: 2014-10-07T21:05:51Z
       
  • Specific and nonspecific effects of biologically active inorganic salts on
           inclusion complex formation of cyclodextrins with aromatic carboxylic
           acids
    • Abstract: Publication date: 27 January 2015
      Source:Chemical Engineering Science, Volume 122
      Author(s): Irina Terekhova , Ekaterina Chibunova , Roman Kumeev , Sergey Kruchinin , Marina Fedotova , Małgorzata Kozbiał , Małgorzata Wszelaka-Rylik , Pawel Gierycz
      Inclusion complex formation of α- and β-cyclodextrins with zwitterionic nicotinic and m-aminobenzoic acids in water and 0.2M solutions of KCl, KBr, KH2PO4 and K2SO4 was studied by 1H NMR and UV-spectroscopy. We complemented the experiments with statistical mechanics calculations in the framework of the 3D-RISM approach to analyze the ion-binding between inorganic univalent anions and positively charged groups of the acids under study. It was detected that binding affinity of cyclodextrins to the acids is decreased in the presence of the salts. This is caused by specific and nonspecific action of the considered inorganic anions. The influence of the Cl− and SO 4 2 − was found to be nonspecific and insignificant. On the contrary, Br− and H 2 PO 4 − ions can considerably affect the inclusion complex formation. Insertion of Br− into the macrocyclic cavity and attraction between H 2 PO 4 − and the zwitterions are the main processes competing with cyclodextrin–acid binding. It has been demonstrated that the manifestation of the salt effects depends on the cyclodextrin cavity size, ionization state of the acid and other experimental conditions.


      PubDate: 2014-10-07T21:05:51Z
       
  • Reduced-order model for the analysis of mass transfer enhancement in
           membrane channel using electro-osmosis
    • Abstract: Publication date: 27 January 2015
      Source:Chemical Engineering Science, Volume 122
      Author(s): Ridwan Setiawan , Pesila Ratnayake , Jie Bao , Gustavo A. Fimbres Weihs , Dianne E. Wiley
      Flow control has the potential to mitigate concentration polarization and fouling in membrane systems by enhancing mixing near the membrane surface. Although Computational Fluid Dynamics (CFD) modeling has been used to study the effect of externally induced unsteady flow on mass transfer enhancement, the analysis based on CFD results is computationally expensive and cannot be performed systematically. Existing systematic approaches to quantify mixing enhancement only consider hydrodynamics but not the direct effect on mass transfer improvement, due to the difficulties caused by the non-spatially invariant nature of the mass transfer phenomenon. This paper presents a reduced-order model that combines the discretized mass transfer and linearized Navier–Stokes partial differential equations. The proposed model can be used to simulate and systematically analyze mass transfer enhancement caused by the flow induced by a pair of electrodes. When the Reynolds number and temporal frequency of the external field are low ( Re < 2000 ), the effect of a forced wall slip velocity on the overall flow profile in a 2D channel can be approximated by its instantaneous component. This allows mass transfer enhancement to be analyzed explicitly using a discretized mass transfer equation. The results predicted by the reduced-order model are in good agreement with CFD simulations. The benefit of the proposed reduced-order model is demonstrated by the frequency response analysis to identify the temporal frequency that has the maximum effect on mass transfer enhancement.


      PubDate: 2014-10-07T21:05:51Z
       
  • Response to comment on “Experimental study of particle separation
           and the fish hook effect in a mini-hydrocyclone” [Chem. Eng. Sci.
           111 (2014) 94–105]
    • Abstract: Publication date: 27 January 2015
      Source:Chemical Engineering Science, Volume 122
      Author(s): Guofeng Zhu , Jong-Leng Liow , Andrew Neely



      PubDate: 2014-10-07T21:05:51Z
       
  • Comment on: ‘Experimental study of particle separation and the fish
           hook effect in a mini-hydrocyclone’ by G. Zhu and J.L. Liow
           [Chemical Engineering Science 111 (2014) 94–105]
    • Abstract: Publication date: 27 January 2015
      Source:Chemical Engineering Science, Volume 122
      Author(s): K. Nageswararao
      Recent report on fish hook effect by Zhu and Liow [Chemical Engineering Science 111(2014) 94–105] involves size analyses using laser diffractometry. Since their test materials contain a significant amount of submicron particles, the refractive index and extinction coefficient of the particles have a major impact on the size analyses results. As such, if correct optical parameters are not used systematic errors in size analyses are inevitable. The data of Zhu and Liow are subject to this uncertainty. As a result, while their size analyses are repeatable, the accuracy is indeterminate. The reproducibility of their data is also questionable. Consequently, their results and conclusions on fish hook are to be treated with caution.


      PubDate: 2014-10-07T21:05:51Z
       
  • Agglomeration of solid particles by liquid bridge flocculants: Pragmatic
           modelling
    • Abstract: Publication date: 27 January 2015
      Source:Chemical Engineering Science, Volume 122
      Author(s): Boris V. Balakin , Guzel Shamsutdinova , Pawel Kosinski
      The present paper proposes a model for agglomeration of solid particles covered with a liquid flocculant. Rather then being derived by time-consuming numerical simulations of collision dynamics as the particles are in contact, the model is based on analytic relations: thus the computational cost is significantly reduced. The model was implemented into a computer code simulating a set of particles using the Eulerian–Lagrangian approach, that is, it forms an attractive alternative to Distinct Element Modelling (DEM). Moreover numerical simulations in a shear-flow system were done and the results were compared with a theoretical model.


      PubDate: 2014-10-07T21:05:51Z
       
  • The generalized coalescence/redispersion micromixing model. A multiscale
           approach
    • Abstract: Publication date: 27 January 2015
      Source:Chemical Engineering Science, Volume 122
      Author(s): Béla G. Lakatos
      The generalised coalescence/redispersion (gCR) micromixing model is formulated in the framework of the three scale mixing concept of stirred tank reactors. It is developed on the basis of a random coefficient differential equation system describing mass exchange interactions between the Kolmogorov scale fluid elements the average behaviour of which is modelled using the population balance approach. The model provides closed terms for both the chemical reactions and micromixing and it allows computing processes with either pre-mixed or unmixed feeds of reactors. A qualitative picture of producing the fluid elements in the eddy space as Kolmogorov microscale eddies, interpreted as mesomixing of the three scale mixing model is outlined. The population balance equation is reduced to a moment equation system for joint moments of concentrations using the standard moment method which is closed by cumulant-neglect closure. The gCR model is validated by fitting the model to literature data of bimolecular quasi-linear chemical reactions (Miyawaki et al., 1975. J. Chem. Eng. Jpn. 8, 63–68; Takao et al., 1978. J. Chem. Eng. Jpn. 11, 481–486), and of a quasi-linear consecutive–competitive chemical reaction system (Paul and Treybal, 1971. AlChE J. 17, 718–724) in stirred tank reactors. It is pointed out by simulation that in case of non-homogeneous micromixing space of stirred tank reactor different inlets–outlet configurations of mixing experiments produce significantly different concentration responses, and using the gCR model micromixing inhomogeneities can be explored.


      PubDate: 2014-10-07T21:05:51Z
       
  • Validation of a new phenomenological “jump-and-channel” model
           for the wet pressure drop of oil mist filters
    • Abstract: Publication date: 27 January 2015
      Source:Chemical Engineering Science, Volume 122
      Author(s): D. Kampa , S. Wurster , J. Meyer , G. Kasper
      The “wet pressure drop” of oil mist filters (i.e. the increase in differential pressure of the air flow due to loading of the filter with liquid) is presented as a function of two mechanisms by which coalesced oil is transported through the filter. These mechanisms operate in separate regions of the filter and make separate (and separately measurable) contributions to the overall wet pressure drop. This new concept, which was first formulated qualitatively in a phenomenological model by Kampa et al. (2014), leads to semi-quantitative predictions regarding the dependence of pressure drop Δp and saturation S on filter operating conditions, filter properties and liquid properties. These predictions are first formulated and then validated for a range of wettable and non-wettable filter media in combination with 4 mineral oils of different viscosity. The key findings, summarized below, are consistent with the model and apply to both wettable and non-wettable media. Oil transport across media interfaces (i.e. transitions between regions of different porosity and/or wettability) was associated with a relatively sharp increase in pressure drop ∆p and oil saturation S over a very thin layer of the filter (a “∆p jump”). The magnitude of this ∆p jump was determined by the media properties. It correlated well with the respective static break-through pressures for oil or air, but did not depend on the oil viscosity and loading rate of the filter (at constant air velocity). Oil transport through channel regions of the filter (i.e. the regions connecting interfaces) was associated with a linear increase in ∆p with channel length and liquid throughput. The corresponding saturation level S was relatively flat throughout the channel region and lower than at an interface. (Both quantities are media dependent, of course.) An increase in oil viscosity μ (at constant oil throughput) led to different responses depending on filter wettability.


      PubDate: 2014-10-07T21:05:51Z
       
  • Metabolic characterization and modeling of fermentation process of an
           engineered Geobacillus thermoglucosidasius strain for bioethanol
           production with gas stripping
    • Abstract: Publication date: 27 January 2015
      Source:Chemical Engineering Science, Volume 122
      Author(s): Hongxing Niu , David Leak , Nilay Shah , Cleo Kontoravdi
      The recently engineered Geobacillus thermoglucosidasius strain is an industrially potent thermophilic ethanologen. We employ a systematic approach to improve our understanding of the fermentation process using cellobiose as the substrate. Dynamic metabolic flux analysis clearly shows that the fluxes from pyruvate to lactate and formate are both strictly constrained throughout the process and that both the maximum ethanol yield (0.46C/C) and the maximum specific productivity (19.8mmolC (gDCW)−1 h−1) occur at late-exponential growth phase. Accordingly, extreme pathway analysis reduces the metabolic network into a macro reaction scheme, on which a dynamic metabolic model is built. The model is validated with experimental data, parameters are identified with confidence intervals, and global sensitivity analysis (Sobol׳ method) is performed. Model-based optimization predicts that ethanol productivity could increase from 34.2 in a typical batch process to 55.3mmolL−1 h−1 in an optimum fed-batch process with higher ethanol yield. Furthermore, the optimal operating regime was identified to be continuous fermentation process with gas stripping, in which a high ethanol productivity of 113mmolL−1 h−1, i.e., 26.8mmolC (gDCW)−1 h−1, corresponding to 90.2% of the maximum theoretical ethanol yield could be achieved.


      PubDate: 2014-10-07T21:05:51Z
       
  • Separation and recovery of nickel, as a salt, from an EDTA leachate of
           spent hydrodesulphurization catalyst using precipitation methods
    • Abstract: Publication date: 27 January 2015
      Source:Chemical Engineering Science, Volume 122
      Author(s): Isabel S.S. Pinto , S.M. Sadeghi , Helena M.V.M. Soares
      The aim of the present work was to recover Ni, as a salt, from an ethylenediaminetetracetic acid (EDTA) solution that also contains Al and Mo, obtained after leaching a spent Ni–Mo hydrodesulphurization catalyst. The pH for EDTA precipitation was optimized in order to maximize further separation of Al and Mo from Ni. At pH=1, 80% of EDTA was precipitated, followed by precipitation of Al and Mo (recovery of 94 and 67%, respectively) at pH 5. From this point, three options for recovering Ni, as a salt, were studied. The first consisted on a second EDTA precipitation at lower pH followed by Ni precipitation, as Ni(OH)2, by increasing the pH; the second and the third ones involved sequential addition of Fe3+ and phosphate ions, with and without the second EDTA precipitation step, respectively. The addition of Fe induces the substitution of Ni in the EDTA complexes, leaving Ni free to precipitate with the phosphate, which maximizes Ni recovery. The highest Ni recovery was 93%, as nickel phosphate, with a purity ≥96% in the sequence involving second EDTA precipitation, where 70% of the remaining EDTA was recovered at pH 0.4, followed by addition of Fe3+ and precipitation as nickel phosphate. However, this option has the highest costs in terms of reagents consumption. By suppressing the second EDTA precipitation step, nickel phosphate was recovered with lower yield and purity (82 and 94%, respectively). In the case, where Ni was precipitated as Ni(OH)2, nickel recovery only reached 70%, with ≥97% purity; still, this possibility has the lowest reagents cost. In the two options that included phosphate addition, the analysis of the obtained solid suggests the Ni3(PO4)2 stoichiometry and the proposed process is clean, with almost no generation of residues, since the precipitated EDTA can be recycled into the leaching stage and the Fe, recovered as a solid, can be reused as an iron source.


      PubDate: 2014-10-07T21:05:51Z
       
  • Structure-dependent multi-fluid model for mass transfer and reactions in
           gas–solid fluidized beds
    • Abstract: Publication date: 27 January 2015
      Source:Chemical Engineering Science, Volume 122
      Author(s): Cenfan Liu , Wei Wang , Nan Zhang , Jinghai Li
      A fluidized bed reactor embraces complex coupling among flow, heat/mass transfer and reaction kinetics over a wide range of spatial-temporal scales, on which the meso-scale structure in forms of bubble or cluster plays the critical role. The traditional two-fluid model (TFM) is based on local equilibrium assumption and neglects the effects of sub-grid meso-scale structures, thus, it is not suitable for simulating dense, heterogeneous gas–solid riser flow. To be consistent with the meso-scale characteristics, we proposed a structure-dependent multi-fluid model (SFM). It reduces to the conventional two-fluid model (TFM) if local equilibrium or homogeneity is assumed within each grid, and reverts to the energy-minimization multi-scale (EMMS) model if it is used to describe global behavior of a fluidized bed. The multiscale CFD based on SFM and EMMS drag has been successfully applied in simulating gas–solid fluidized bed flows in recent years. In this work, we will extend such approach to the realm of reactive flows with mass transfer and reactions. The heterogeneity indexes for reaction and mass transfer are thereby defined, which may facilitate TFM-based reactive simulations with structure-dependent corrections. Two experiments of ozone decomposition in circulating fluidized beds are simulated to validate this approach with comparison to data.


      PubDate: 2014-10-07T21:05:51Z
       
  • Controllable modification of polymer membranes by LDDLT plasma flow:
           membrane module scale-up and hydrophilic stability
    • Abstract: Publication date: 27 January 2015
      Source:Chemical Engineering Science, Volume 122
      Author(s): Mei-Sheng Li , Zhi-Ping Zhao , Ming-Xing Wang
      The modification of PE hollow fibers in a module scale was carried out by long-distance and dynamic low-temperature (LDDLT) plasma flow, which is an environment-friendly surface chemical engineering method. For the module with a plasma inlet diameter of 15mm, contact angle variations along with fiber axial distance from plasma inlet revealed that the effective modification distance by LDDLT plasma flow was easily scaled up to about 80cm for purpose of industrial applications. The plasma-treated membrane module (PTMM) exhibited not only good chemical resistance in various solutions but also excellent antifouling property and hydrophilic stability. Moreover, the PTMM, which was dried at 25°C in vacuum after each filtration cycle, could still maintain high hydrophilicity after 7 water filtration cycles and storing over 90 days. Its average contact angle recovered by only 7°, and the steady water flux was about 30Lm−2 h−1, far higher than the untreated ones.


      PubDate: 2014-10-07T21:05:51Z
       
  • [C4H8SO3Hmim]HSO4 as an efficient catalyst for direct liquefaction of
           bagasse lignin: Decomposition properties of the inner structural units
    • Abstract: Publication date: 27 January 2015
      Source:Chemical Engineering Science, Volume 122
      Author(s): Jinxing Long , Wenyong Lou , Lefu Wang , Biaolin Yin , Xuehui Li
      Catalytic valorization of renewable aromatic lignin is attracting increasing attention. In this study, an efficient method for direct liquefaction of sugarcane bagasse lignin using acidic ionic liquid (IL) 1-(4-sulfobutyl)-3-methyl imidazolium hydrosulfate ([C4H8SO3Hmim]HSO4) is presented. The relationships between catalyst dosage, reaction condition parameters and degree of liquefaction, and the structure and elemental composition of liquefaction residue were investigated. The transformation performances of three molecular structural units (guaiacyl, syringyl, and hydroxyphenyl units) of bagasse lignin were also intensively examined using gas chromatography-mass spectrometry, elemental analysis, Fourier transform infrared spectrometry, and proton nuclear magnetic resonance characterization. The results demonstrated that the dual-functionalized acidic IL exhibited excellent catalytic performance in the direct liquefaction process. More than 65% degree of liquefaction was achieved under optimized conditions, yielding 13.5% of useful aromatic fine chemicals such as phenol, 4-ethylphenol, and guaiacol. The p-hydroxyphenyl unit of lignin was the most flexible, followed by the guaiacyl unit, whereas the syringyl group was the most refractory. Furthermore, the catalytic mechanism was proposed.
      Graphical abstract image

      PubDate: 2014-10-02T20:49:43Z
       
  • Viscoelastic fluid behaviors around a rising bubble via a new method of
           mesh deformation tracking
    • Abstract: Publication date: 16 December 2014
      Source:Chemical Engineering Science, Volume 120
      Author(s): Yuya Imaizumi , Tomoaki Kunugi , Takehiko Yokomine , Zensaku Kawara
      The deformation of a hydrogen microbubble line and/or mesh in a viscoelastic fluid around a rising bubble was tracked from the original static position in order to discuss the mechanism of the typical phenomena such as the negative wake or the cusp shape. This new experimental method is essentially important because of the hysteresis-dependent nature of the viscoelastic fluid. This new method makes this study distinctive from a number of conventional studies of viscoelastic fluids focusing on the non-Newtonian properties and/or the instantaneous flow field. According to our experimental results, the flow mechanism responsible for the negative wake or cusp shape was attributed to the accumulation and release of the shear strain energy. Some residual displacements were observed after the bubble rising, which were almost completely reproduced as the internal dissipations in a Maxwell model modified with a non-linear spring.


      PubDate: 2014-10-02T20:49:43Z
       
  • Kinetics of the reduction of wüstite by hydrogen and carbon monoxide
           for the chemical looping production of hydrogen
    • Abstract: Publication date: 16 December 2014
      Source:Chemical Engineering Science, Volume 120
      Author(s): Wen Liu , Jin Yang Lim , Marco A. Saucedo , Allan N. Hayhurst , Stuart A. Scott , J.S. Dennis
      Hydrogen of very high purity can be produced via the steam-iron process, in which steam oxidises metallic Fe in 3/4Fe+H2O→1/4Fe3O4+H2. It is then advantageous to oxidise Fe3O4 in air to Fe2O3, an oxygen-carrier. This higher oxide of Fe is then reduced to regenerate metallic iron by reacting with synthesis gas, producing metallic Fe and possibly some wüstite (Fe x O, 0<x<1). In this three-stage process, the reduction of Fe x O to Fe is the slowest reaction. This paper is concerned with the kinetics of the reduction of wüstite (Fe x O) by reaction with CO, and, or H2. Starting with pure (99wt%) wüstite, the intrinsic kinetics of its reduction to metallic iron were measured in fluidised beds at different temperatures. The reaction was found to have 3 distinct stages, (i) the removal of lattice oxygen in wüstite, (ii) rate increasing with conversion of solid and (iii) rate decreasing with conversion of solid. A random pore model was used to simulate the latter stages of the reduction of wüstite by either H2 or CO or a mixture of the two. It was found that the intrinsic rate of reduction in H2 is substantially faster than with CO, whereas the resistances to diffusion of H2 and CO through the product layer of Fe are comparable; these factors account for differences in the overall rates observed with these gases.


      PubDate: 2014-10-02T20:49:43Z
       
  • Transient simulation for large scale flow in bubble columns
    • Abstract: Publication date: 27 January 2015
      Source:Chemical Engineering Science, Volume 122
      Author(s): T. Ziegenhein , R. Rzehak , D. Lucas
      The transient simulation of large scale bubbly flow in bubble columns using the unsteady Reynolds averaged Navier Stokes (URANS) equations is investigated in the present paper. An extensive set of bubble forces is used with different models for the bubble induced turbulence. Criteria are given to assess the independence of the simulation time and the time step length. Using these criteria it is shown that a simulation time, time step length and mesh independent solution can be obtained for complex bubbly flows using URANS equations under certain requirements. With the obtained setup the contribution of the resolved turbulence to the total turbulence and the influence of the bubble induced turbulence modeling on the resolved turbulence is investigated. Further, it is pointed out that the virtual mass force is not negligible. The simulations are compared to data from the literature at two different superficial velocities, which cover monodisperse and polydisperse bubbly flows.


      PubDate: 2014-10-02T20:49:43Z
       
  • A computationally simple technique for analyzing catalyst inhibition
           dynamics involving multiple competing inhibitors
    • Abstract: Publication date: 16 December 2014
      Source:Chemical Engineering Science, Volume 120
      Author(s): Benjamin S. White , Teh C. Ho
      In catalyst development a targeted reaction often is inhibited by strongly adsorbed species that are present in the feed. To develop means of mitigating the inhibition effect, it is important to gain a predictive understanding of the inhibition dynamics from modeling of transient response experiments. This approach can also be used for catalyst characterization and mechanistic kinetics studies. Accordingly, this work considers a general class of catalyst inhibition problems involving m competing inhibitors in fixed-bed reactors under non-equilibrium conditions. A mathematical model consisting of a system of 2m+1 nonlinear hyperbolic partial differential equations is reduced to that of 2m first-order ordinary differential equations. The result is an efficient method for discriminating rival models and extracting active site densities and adsorption-reaction rate constants from transient response data.


      PubDate: 2014-10-02T20:49:43Z
       
  • P84 polyimide membranes modified by a tripodal amine for enhanced
           pervaporation dehydration of acetone
    • Abstract: Publication date: 27 January 2015
      Source:Chemical Engineering Science, Volume 122
      Author(s): Dave W. Mangindaan , Nelson Minyang Woon , Gui Min Shi , Tai Shung Chung
      In this work we have fabricated P84 asymmetrical flat sheet membranes with a sponge-like structure by carefully formulating the polymer dope, followed by crosslinking the P84 membranes with a tripodal amine (tris(2-aminoethyl)amine (TAEA)) in a methanol solution, combined with heat treatment. The separation performances for acetone dehydration as functions of dope formulation, TAEA crosslinking time and post-annealing duration were further investigated and optimized by using the Taguchi statistical method. The membrane with the best pervaporation performance possessed a high separation factor of 983 with a reasonable flux of 0.658kgm−2 h−1. FESEM, FTIR and XPS were employed to elucidate the crosslinking mechanisms and explain the evolution of physicochemical properties and chemistry–performance relationship. A benchmark comparison indicates that the newly developed P84/TAEA crosslinked membrane has good separation performance for acetone dehydration.


      PubDate: 2014-10-02T20:49:43Z
       
  • Metal organic framework membranes for carbon dioxide separation
    • Abstract: Publication date: 16 December 2014
      Source:Chemical Engineering Science, Volume 120
      Author(s): Surendar R. Venna , Moises A. Carreon
      In this paper we review research progress on metal organic framework membranes which have demonstrated ability to separate carbon dioxide from different light gases. More specifically, we focus mainly on CO2/N2, CO2/CH4, and CO2/H2, gas separations which are highly relevant compositions in flue gas treatment, natural gas purification, and hydrogen purification, respectively. We also discuss several conventional and novel strategies developed by several research groups for the continuous defect-free MOF membrane fabrication. Finally, the advantages of using MOFs in mixed matrix membranes and improvements in gas separation performances with the MOF based mixed matrix membranes are presented.
      Graphical abstract image

      PubDate: 2014-10-02T20:49:43Z
       
  • Enhanced carbon dioxide hydrate formation kinetics in a fixed bed reactor
           filled with metallic packing
    • Abstract: Publication date: 27 January 2015
      Source:Chemical Engineering Science, Volume 122
      Author(s): Asheesh Kumar , Tushar Sakpal , Praveen Linga , Rajnish Kumar
      In this fundamental work, two nonporous metallic (SS-316) mesh arrangements having high thermal conductivity compared to silica sand and silica gel were used as a packing material in a fixed bed setup for faster hydrate growth kinetics. Induction time and kinetics of carbon dioxide hydrate formation was investigated at 3.0MPa and 274.65K. An anionic surfactant, 1wt% sodium dodecyl sulfate (SDS) was used as a kinetic promoter in all the experiments. Significantly higher gas uptake rate of 115molmin−1 m−3 and water to hydrate conversion of 50% was achieved in an hour of hydrate formation with metallic packing in the presence of SDS. Amount of CO2 gas captured per mass/volume of packing material was significantly higher for metallic packing compared to silica sand and silica gel, which is an important parameter for evaluating a hydrate crystallization process using fixed bed.


      PubDate: 2014-10-02T20:49:43Z
       
  • Two-dimensional non-equilibrium model of liquid chromatography: Analytical
           solutions and moment analysis
    • Abstract: Publication date: 27 January 2015
      Source:Chemical Engineering Science, Volume 122
      Author(s): Sadia Parveen , Shamsul Qamar , Andreas Seidel-Morgenstern
      This paper presents a set of semi-analytical solutions and analytical moments for two-dimensional lumped kinetic model (LKM) describing non-equilibrium solute transport through a chromatographic column of cylindrical geometry. General solutions are derived for the solute concentration by successive implementation of finite Hankel and Laplace transforms assuming different sets of boundary conditions and linear sorption kinetic process. For further analysis, statistical temporal moments are derived from the Laplace transformed solutions. The current solutions extend and generalize the recent solutions of two-dimensional equilibrium dispersive transport model (EDM). Typical examples of concentration profiles and moments resulting from different sets of initial and inlet conditions are presented and briefly discussed. The derived semi-analytical solutions for concentration profiles and analytical moments are validated against the numerical results of a high resolution finite volume scheme. Good agreements in the results verify the correctness of analytical solutions and accuracy of the proposed numerical algorithm.


      PubDate: 2014-10-02T20:49:43Z
       
  • Detailed simulation of dual-reflux pressure swing adsorption process
    • Abstract: Publication date: 27 January 2015
      Source:Chemical Engineering Science, Volume 122
      Author(s): Tushar S. Bhatt , Giuseppe Storti , Renato Rota
      A model for the detailed simulation of dual-reflux pressure swing adsorption process developed in the frame of the commercial software Aspen Adsim® is presented. For validation purposes, simulations were performed and model predictions were compared with published experimental results. At cyclic steady-state, model predictions were found to be in good agreement with reported experimental results in terms of (i) average ethane mole fraction in heavy product, (ii) average nitrogen mole fraction in light product, (iii) instantaneous heavy product composition profiles, and (iv) instantaneous column composition profiles. The predicted and experimental trends obtained by analyzing the effect of various operating parameters (light reflux flowrate, duration of feed/purge step, heavy product flowrate and mole fraction of heavy component in binary feed gas mixture) on process performance are also comparable. Overall, this simulation technique of dual-reflux pressure swing adsorption can serve as an effective tool for process design, cost reduction of laboratory and/or plant trails, and enhanced process understanding.


      PubDate: 2014-10-02T20:49:43Z
       
  • Unification of EMMS and TFM: structure-dependent analysis of mass,
           momentum and energy conservation
    • Abstract: Publication date: 16 December 2014
      Source:Chemical Engineering Science, Volume 120
      Author(s): Feifei Song , Wei Wang , Kun Hong , Jinghai Li
      The two-fluid model (TFM) has been widely applied in simulation of various multiphase flow systems. In particular, for fine-particle circulating fluidization, the drag force plays a critical role whereas the classic drag models based on empirical correlations of homogeneous fluidization are found inadequate. Therefore, various approaches have been proposed in recent years to account for the effects of meso-scale structure on the drag force, in which the energy-minimization multi-scale model (EMMS) has received rapidly growing applications. However, the relationship between the TFM and EMMS has not been clarified to enable their combination. To solve this problem, we present a structure-dependent analysis of mass, momentum and energy conservation equations. This analysis is rooted in the structure-dependent multi-fluid model (SFM), which details the composition of drag forces and energy consumptions and their relationships with consideration of meso-structures. With assumption of homogeneous structures, it reduces to the TFM equations; for steady-state systems with structures, it restores the force balance equations, equal pressure drop relation and energy relationship of the EMMS. In future, the scale dependence of this analysis deserves more efforts to understand the applicability of the EMMS stability condition on different scales.


      PubDate: 2014-09-25T20:29:04Z
       
  • Table of Contents
    • Abstract: Publication date: 8 November 2014
      Source:Chemical Engineering Science, Volume 119




      PubDate: 2014-09-25T20:29:04Z
       
  • Computational exploration of metal–organic frameworks for CO2/CH4
           separation via temperature swing adsorption
    • Abstract: Publication date: 16 December 2014
      Source:Chemical Engineering Science, Volume 120
      Author(s): Zhengjie Li , Gang Xiao , Qingyuan Yang , Yuanlong Xiao , Chongli Zhong
      Molecular simulations were performed to investigate the performance of 151 metal–organic frameworks (MOFs) with large chemical and topological diversity on CO2/CH4 separation via temperature swing adsorption (TSA) process. The thermal regeneration energy was adopted in this work as an evaluation criterion and combined with other three commonly used ones (CO2 working capacity, adsorption selectivity and regenerability) to explore the structure–property relationships for the separation of the target system. The results show that the four evaluation criteria exhibit intimate correlations with the difference of adsorbility ( Δ A D ) of adsorbates but with non-concerted changing tendency. With a certain range of this parameter, it can be used as a good indicator for the preliminary screening of MOFs and the tailoring of new materials. Furthermore, from the structural database considered in current study, Cu-TDPAT with strong CO2 adsorption sites was found to possess the best performance by taking the thermal and water-stable properties into account.


      PubDate: 2014-09-21T20:24:40Z
       
  • EMMS-based discrete particle method (EMMS–DPM) for simulation of
           gas–solid flows
    • Abstract: Publication date: 16 December 2014
      Source:Chemical Engineering Science, Volume 120
      Author(s): Liqiang Lu , Ji Xu , Wei Ge , Yunpeng Yue , Xinhua Liu , Jinghai Li
      Understanding the hydrodynamics of gas–solid flows is a grand challenge in mechanical and chemical engineering. The continuum-based two-fluid models (TFM) are currently not accurate enough to describe the multi-scale heterogeneity, while the discrete particle method (DPM) following the trajectory of each particle is computationally infeasible for industrial systems. Following our previous work, we report in this article a coarse-grained DPM considering the meso-scale structure based on the energy-minimization multi-scale (EMMS) model, which can be orders of magnitude faster than the traditional DPM and can take full advantage of CPU–GPU (graphics processing unit) hybrid supercomputing. The size and solids concentration of the coarse-grained particles (CGP), as well as their interactions with the gas flow (the drag) are determined by the EMMS model with a two-phase decomposition. The interactions between CGPs are determined according to the kinetic theory of granular flows (KTGF). The method is tested by simulating the onset of fluidization and the steady state flow in lab-scale circulating fluidized bed (CFB) risers with different geometries and operating conditions both in 2D and 3D. The results agree well with experiments and traditional DPM based on single particles. The prospect of this method as a higher-resolution alternative to TFM for engineering applications and even for virtual process engineering is discussed finally.
      Graphical abstract image

      PubDate: 2014-09-21T20:24:40Z
       
  • Electro-coalescence of water drops in oils under pulsatile electric fields
    • Abstract: Publication date: 16 December 2014
      Source:Chemical Engineering Science, Volume 120
      Author(s): S.H. Mousavi , M. Ghadiri , M. Buckley
      Electric fields are commonly used to enhance the coalescence of water drops in oils. However, this process could cause some undesirable phenomena such as secondary droplets formation, reducing the separation efficiency. Here the effect of pulsatile electric fields (PEF) on the secondary droplets formation has been investigated. In the presence of a very low frequency PEF or DC electric field three distinct drop–drop and drop–interface interaction patterns are observed: complete coalescence, partial coalescence and rebound without coalescence. The first is the ideal pattern not leaving any secondary droplets. It has previously been shown that an increase in the electric field strength and/or a decrease in the interfacial tension result in non-ideal patterns in drop–interface coalescence. The application of PEF shifts the coalescence pattern from a non-ideal to an ideal one in both drop–drop and drop–interface coalescences. Three waveform types, i.e. square, half-sinusoidal and sawtooth waves have been applied to the coalescence process. It is shown that the sawtooth waveform is the most effective in reducing the secondary droplets formation in drop–interface coalescence, followed closely by the half-sinusoidal one. The observation of videos sequences suggests that a threshold frequency exists above which a non-ideal pattern switches to an ideal one. For drop–drop coalescence this threshold frequency depends on the PEF amplitude and the size of primary drop pairs, as for bigger primary drop pairs and larger amplitudes of PEF the threshold frequency would be higher. When using pulsatile electric fields higher field strengths can be applied for systems having high water content without causing field breakdown, as compared to the constant DC field. This is useful in optimizing the electro-coalescence process.


      PubDate: 2014-09-21T20:24:40Z
       
  • Numerical simulations of lateral solid mixing in gas-fluidized beds
    • Abstract: Publication date: 16 December 2014
      Source:Chemical Engineering Science, Volume 120
      Author(s): Oyebanjo Oke , Paola Lettieri , Piero Salatino , Roberto Solimene , Luca Mazzei
      We investigated the influence of design parameters and operational conditions on lateral solid mixing in fluidized beds adopting the Eulerian-Eulerian modeling approach. To quantify the rate at which solids mix laterally, we used a lateral dispersion coefficient ( D s r ). Following the usual approach employed in the literature, we defined D s r by means of an equation analogous to Fick׳s law of diffusion. To estimate D s r , we fitted the void-free solid volume fraction radial profiles obtained numerically with those obtained analytically by solving Fick׳s law. The profiles match very well. Our results show that D s r increases as superficial gas velocity and bed height increase; furthermore, it initially increases with bed width, but then remains approximately constant. The values of D s r obtained numerically are larger than the experimental ones, within the same order of magnitude. The overestimation has a twofold explanation. On one side, it reflects the different dimensionality of simulations (2D) as compared with real fluidized beds (3D), which affects the degrees of freedom of particle lateral motion. On the other, it is related to the way frictional solid stress was modeled: we employed the kinetic theory of granular flow model for the frictional solid pressure and the model of Schaeffer (1987) for the frictional solid viscosity. To investigate how sensitive the numerical results are on the constitutive model adopted for the frictional stress, we ran the simulations again using different frictional models and changing the solid volume fraction at which the bed is assumed to enter the frictional flow regime ( ϕ m i n ) . We observed that D s r is quite sensitive to the latter. This is because this threshold value influences the size and behavior of the bubbles in the bed. We obtained the best predictions for ϕ m i n = 0.50 . The results show that accurate prediction of lateral solid dispersion depends on adequate understanding of the frictional flow regime, and accurate modeling of the frictional stress which characterizes it.


      PubDate: 2014-09-21T20:24:40Z
       
  • Prediction of the mixing behaviour of binary mixtures of particles in a
           bladed mixer
    • Abstract: Publication date: 16 December 2014
      Source:Chemical Engineering Science, Volume 120
      Author(s): M. Halidan , G.R. Chandratilleke , S.L.I. Chan , A.B. Yu , J. Bridgwater
      The effects of particle size and density on the mixing behaviour of binary mixtures of spheres in a vertically-shafted bladed mixer are studied by means of the discrete element method. To characterise the mixing behaviour, a particle scale mixing index is used. The results reveal that for a given volume fraction, there are optimum small-to-large size ratio and light-to-heavy density ratio that can provide the maximum mixing index. That is, the particle size and density differences can interact with each other, sometimes improving mixing. The mechanism behind this mixing improvement is confirmed by the analysis of vertical forces on particles. The improvement occurs because large-heavy particles can sink to the vessel base under their heavy weight instead of being pushed upwards by the vertical force generated due to the size-difference. Small-light particles move on top of the large particles, improving the mixing behaviour. The volume fraction of the mixing particles also affects the mixing behaviour. The effects of particle size, density and volume fraction can be quantified in detail, and an empirical predictive equation to describe these effects is established for this purpose based on the simulated results. The equation can be used to determine the particle size and density ratios that result in an identical mixing quality, generating a comprehensive picture about the size and density equivalence in relation to mixing. Such a quantitative description is promising in application in that the present mixing system with its simple geometry can be used as a standard reference mixer for quantifying the effects of particle properties.


      PubDate: 2014-09-21T20:24:40Z
       
  • Flooding limit in countercurrent gas–liquid structured packed
           beds—Prediction from a linear stability analysis of an Eulerian
           two-fluid model
    • Abstract: Publication date: 16 December 2014
      Source:Chemical Engineering Science, Volume 120
      Author(s): I. Iliuta , F. Larachi , M. Fourati , L. Raynal , V. Roig
      Countercurrent flooding limits in gas–liquid structured packed bed columns were studied using a stability analysis of the solutions of a transient two-zone two-fluid hydrodynamic model around a uniform state. The model is based on the volume-average mass and momentum balance equations and the double-slit drag closures. The source terms in momentum balance equations refer to the total phase interaction and mechanical dispersion forces and the closure expression relating the gas and liquid pressures is given by capillary dispersion and gravity. The model predicts very well the flooding limits for air–water countercurrent flow through various Mellapak structured packings. The incidence on the column-limited flooding point of packing geometry (porosity and specific surface area), fluid throughputs and properties (viscosity, gas and liquid densities) and liquid spreading characteristics was discussed from the perspective of model simulated trends. Gravity was unveiled as the most important factor in the stabilization force which contributes to the attenuation of liquid waves inducing a tendency to make the flow more uniform. Its contribution was factored in using a modified capillary pressure model. Beside gravity, this formulation indicated that the stabilizing role of capillary forces could not be disregarded, particularly for lower values of the gravity scaling factor in liquid-rich regions at relatively high liquid flow rates.


      PubDate: 2014-09-21T20:24:40Z
       
  • A generalization of the virtual components concept for numerical
           simulation of multi-component isotope separation in cascades
    • Abstract: Publication date: 16 December 2014
      Source:Chemical Engineering Science, Volume 120
      Author(s): Shi Zeng , Lu Cheng , Dongjun Jiang , Valentin Borisevich , Georgy Sulaberidze
      The total flow of the optimal isotope separation cascade should be kept at a minimum to ensure economic viability. The concept of virtual components has proven useful in optimizing and designing cascades for multi-component isotope separation, but is only used in cases with an available analytical solution. Practical situations are complicated and resort to numerical simulations because there are no analytical solutions. Therefore, a generalization for numerical methods is required. A major difficulty in generalization is that mass conservation requires the concentration of a virtual component to be zero, which causes numerical problems. This paper proposes an approach to overcome this difficulty and develops a numerical method accordingly. The matched-R cascade is used as an example for numerical experiments to show that a cascade is solely determined by the choice of the two virtual components, and to demonstrate how the numerical method is applied to find the optimal cascade.


      PubDate: 2014-09-21T20:24:40Z
       
  • A comprehensive study on the kinetics, mass transfer and reaction
           engineering aspects of solvent-free glycerol hydrochlorination
    • Abstract: Publication date: 16 December 2014
      Source:Chemical Engineering Science, Volume 120
      Author(s): Cesar A. de Araujo Filho , Kari Eränen , Jyri-Pekka Mikkola , Tapio Salmi
      The thorough kinetic study of the solvent-free hydrochlorination of glycerol using gaseous hydrogen chloride in a laboratory-scale semibatch reactor was carried out. A wide set of experiments was performed where reaction temperature (70–120°C), catalyst concentration (0–50% by moles) and partial pressure (0.25, 0.5, 0.75 and 1.0atm) were varied. Acetic acid was used as a homogenous catalyst. A more accurate approach was given to the semibatch reactor modeling since it was demonstrated that the liquid volume significantly increased along the reaction. The concentration of HCl was determined experimentally and it was possible to observe the influence of the reaction parameters on the HCl uptake. It was also evidenced that a non-catalytic hydrochlorination takes place in the system and its effect is non-negligible, especially at high temperatures. A new kinetic model was proposed and tested in order to explain the experimental observations. Non-linear regression analysis was successfully applied on the experimental data and the modeling results showed a satisfactory agreement. The model was able to estimate the activation energies for both catalyzed and non-catalyzed experiments. A new concept named Catalyst Modulus was derived from the kinetic equations and then verified with experimental data; the fit of this parameter was very high, thus, pointing out the validity of the model.


      PubDate: 2014-09-21T20:24:40Z
       
  • Performance study of composite silica gels with different pore sizes and
           different impregnating hygroscopic salts
    • Abstract: Publication date: 16 December 2014
      Source:Chemical Engineering Science, Volume 120
      Author(s): X. Zheng , T.S. Ge , R.Z. Wang , L.M. Hu
      Composite solid desiccant materials are fabricated by impregnating hygroscopic salts into pores of different silica gels. In this paper, sorption characteristics of composite desiccants with different pore sizes (namely, 2–3nm, 7–8nm and 9–10nm) of silica gels and different salts in terms of LiCl, LiBr and CaCl2 are tested and analyzed. Researches on nitrogen adsorption suggest that, due to impregnated salt particles, composite desiccants are different from those of pure silica gels and have smaller surface area and pore volume. Sorption isotherms and sorption kinetics with respect to different composite desiccant materials are tested and fitted with the Dubinin–Astakhov (D–A) equation and the Linear Driving Force (LDF) model, respectively. Results showed that both the pore size of silica gel substrates and categories of impregnated salts affect the sorption characteristics of composite desiccants. Microporous silica gel with pore size of 2–3nm is not fit for preparing composite desiccants due to decreased water sorption quantity and sorption rate. Type B and mesoporous silica gels can be a promising host matrix of composite desiccant owing to enhanced water sorption quantity and favorable sorption rate. In addition, composite desiccants employing LiCl have the best sorption properties, while CaCl2 and LiBr follow next.


      PubDate: 2014-09-17T20:16:23Z
       
  • New structure-based model for Eulerian simulation of hydrodynamics in
           
    • Abstract: Publication date: 16 December 2014
      Source:Chemical Engineering Science, Volume 120
      Author(s): A.H. Ahmadi Motlagh , John R. Grace , Martha Salcudean , C.M. Hrenya
      The well-documented inaccuracy of conventional two-fluid modeling of hydrodynamics in fluidized beds of Geldart Group A particles is revisited. A new force-balance (FB) sub-grid-scale model, applied to the conventional Wen–Yu drag correlation, analyzes the balance of van der Waals, drag, gravity and buoyancy forces. It predicts formation of agglomerates inside the bed, updating the drag calculations by applying a correction factor to the conventional drag models to account for agglomerate formation. Good predictions were obtained of fluidization regimes and bed expansion, and there was promising agreement with experimental time-average radial voidage profiles reported by Dubrawski et al. (2013). Good quantitative agreement between DEM and two-fluid predictions of minimum bubbling velocity was also observed when the model was used to predict minimum bubbling velocity, in contrast to the predictions from a non-cohesive, Wen–Yu model. Further evaluation studies are required to test the ability of the new model to predict the properties of larger-scale fluidized beds.


      PubDate: 2014-09-17T20:16:23Z
       
  • Comparison of full-loop and riser-only simulations for a pilot-scale
           circulating fluidized bed riser
    • Abstract: Publication date: 16 December 2014
      Source:Chemical Engineering Science, Volume 120
      Author(s): Tingwen Li , Jean-François Dietiker , Lawrence Shadle
      In this paper, both full-loop and riser-only simulations of a pilot-scale circulating fluidized bed (CFB) system carried out by the open-source code MFIX (Multiphase Flow with Interphase eXchanges) are presented. Detailed comparison between full-loop and riser-only numerical simulations has been conducted with respect to the flow hydrodynamics inside the riser. The mean solids circulation rate is found to be the most critical parameter for both riser-only and full-loop simulations. On one hand, the mean solids circulation rate is needed for specifying the solids inlet boundary condition for the riser-only simulation. On the other hand, a reasonable prediction of the solids circulation rate is a prerequisite for the full-loop simulation to properly predict the flow hydrodynamics inside the riser. To better account for the full-loop dynamics in the riser-only simulation, the transient solids circulation rate measured from an experimental facility is imposed in the simulation in addition to the mean solids circulation rate. Consistent numerical predictions of the flow hydrodynamics inside the riser are obtained by different types of simulations. In-depth discussion on the advantage and disadvantages of each approach is presented and the riser-only simulation with appropriate boundary conditions is shown to be sufficient for investigating the steady CFB riser flow. The full-loop simulation is promising but more challenging as all major components and associated complicated physics have to be included and correctly modeled which require both advanced model capability and high computer power.


      PubDate: 2014-09-17T20:16:23Z
       
  • Analysis of solid concentration distribution in dense solid–liquid
           stirred tanks by electrical resistance tomography
    • Abstract: Publication date: 8 November 2014
      Source:Chemical Engineering Science, Volume 119
      Author(s): Claudio Carletti , Giuseppina Montante , Tapio Westerlund , Alessandro Paglianti
      The knowledge of the spatial solids distribution is important for predicting the performance of various processes carried out in mechanically stirred equipment. In this work, the solid suspension in a stirred tank equipped with PBT and Lightnin A310 impellers is investigated by electrical resistance tomography (ERT). The analysis concerns dense solid–liquid systems, with mass ratio of suspended solid to liquid up to 0.43, with the main goal of obtaining detailed information on the spatial distribution of the dispersed phase and on the mixing quality. The shape of the interface between the solid mixture and the clear liquid layer is also determined. The results provide insight into the complex behaviour of dense suspensions and can be adopted as a benchmark for advanced modeling techniques based on CFD methods. Based on the experimental results, a method for the evaluation of the distribution of the solids under different working conditions and geometrical set-up is suggested. This criterion can provide a guideline for scale-up, when equal solid distribution at different scales is required.


      PubDate: 2014-09-04T19:42:16Z
       
  • Off-line optimization of baker׳s yeast production process
    • Abstract: Publication date: 8 November 2014
      Source:Chemical Engineering Science, Volume 119
      Author(s): Anne Richelle , Philippe Bogaerts
      A macroscopic model describing the influence of nitrogen on a fed-batch baker׳s yeast production process was used for the determination of optimal operating conditions in the sense of a production criterion. To this end, two different approaches were used: a control vector parameterization approach with mesh refinement and an approach based on the mathematical analysis of optimal operating policy (semi-analytical approach). The results of the two approaches lead to the determination of similar optimal operation conditions, which have been implemented for a new experimental phase. Moreover, these optimal conditions are in agreement with the profiles obtained by industrial manufacturers through an empirical optimization of the process (trial and error method). The model predictions are in good accordance with experimental data. This conclusion was supported by an uncertainty analysis on the model outputs with respect to the parameter estimation errors.


      PubDate: 2014-09-04T19:42:16Z
       
  • Crystal shape and size control using a plug flow crystallization
           configuration
    • Abstract: Publication date: 8 November 2014
      Source:Chemical Engineering Science, Volume 119
      Author(s): Joseph Sang-Il Kwon , Michael Nayhouse , Gerassimos Orkoulas , Panagiotis D. Christofides
      This work focuses on modeling and control of a continuous plug flow crystallizer (PFC) used to produce tetragonal hen-egg-white (HEW) lysozyme crystals and proposes an optimization-based control scheme to produce crystals with desired size and shape distributions in the presence of disturbances. Initially, a kinetic Monte Carlo (kMC) model is developed to simulate the crystal growth in a seeded PFC, which consists of five distinct segments. The crystal growth rate equations taken from (Durbin and Feher, 1986) are used in the kMC simulations for the modeling of the crystal growth in the direction of (110) and (101) faces. Then, a population balance equation (PBE) is presented to describe the spatio-temporal evolution of the crystal volume distribution of the entire crystal population, and the method of moments is applied to derive a reduced-order moment model. Along with the mass and energy balance equations, the leading moments that describe the dominant dynamic behavior of the crystal volume distribution are used in the optimization-based controller to compute optimal jacket temperatures for each segment of the PFC and the optimal superficial velocity, in order to minimize the squared deviation of the average crystal size and shape from the set-points throughout the PFC. Furthermore, a feed-forward control (FFC) strategy is proposed to deal with feed flow disturbances that occur during the operation of the PFC. Using the proposed optimization and control schemes, crystals with desired size and shape distributions are produced in the presence of significant disturbances in the inflow solute concentration and size distribution of seed crystals.


      PubDate: 2014-09-04T19:42:16Z
       
  • Preparation of proteolytic microreactors by freeze-drying immobilization
    • Abstract: Publication date: 8 November 2014
      Source:Chemical Engineering Science, Volume 119
      Author(s): Kyuya Nakagawa , Akihiro Tamura , Chaiyan Chaiya
      Protease from Bacillus licheniformis was immobilized in a freeze-dried poly(vinyl alcohol) (PVA) micromonolith directly prepared in the microchannels of a microreactor. The prepared PVA micromonoliths had porous microstructures of ~10–30μm in size. Five microreactors were prepared, with microchannels consisting of interconnected straight and elbow segments or a plain straight segment. The system performance was characterized in terms of proteolytic reaction activities. The reactors demonstrated continuous proteolytic activity for 9d with considerable reaction yields. The proteolytic performance was significantly influenced by the microchannel patterning, and was closely linked to the pressure drops in the reactors. The product distributions varied depending on the flow rates of the substrate solutions and the microchannel patterns. Fractions obtained from different reactors gave different product compositions even when operating under similar conditions and producing comparable yields.


      PubDate: 2014-09-04T19:42:16Z
       
  • Absorption of steam bubbles in lithium bromide solution
    • Abstract: Publication date: 8 November 2014
      Source:Chemical Engineering Science, Volume 119
      Author(s): Philip Donnellan , Kevin Cronin , William Lee , Shane Duggan , Edmond Byrne
      Absorption heat transformers are thermodynamic cycles that are capable of recycling waste heat energy by increasing its temperature. One of the most important unit operations in a heat transformer is the exothermic absorption of water vapour into a solution of choice at a higher temperature. Bubble columns are potentially an efficient means of achieving this. An experimental analysis is conducted which examines the absorption of single steam bubbles into a concentrated aqueous lithium bromide solution. The bubbles are tracked using a high speed camera, and their rate of absorption is modelled using a simple ordinary differential equation model. Accurate model predictions are obtained when oscillating bubble Nusselt and the Sherwood number correlations are utilised. The proposed model is capable of describing 96% of the observed experimental variability. Very large mass transfer coefficients of approximately 0.0012m/s are obtained, which is higher than any previously reported values used in heat transformer absorber design.


      PubDate: 2014-09-04T19:42:16Z
       
  • Analysis of mixing of impinging radial jets with crossflow in the regime
           of counter flow jet formation
    • Abstract: Publication date: 8 November 2014
      Source:Chemical Engineering Science, Volume 119
      Author(s): Е.V. Kartaev , V.А. Emel’kin , М.G. Ktalkherman , V.I. Kuz’min , S.М. Aul’chenko , S.P. Vashenko
      Experimental investigation and numerical calculation of the macromixing of multi-orifice impinging radial jets and main crossflow in the plasma-chemical reactor channel were performed. The emphasis is on the analysis of the conditions providing the formation of a jet on the channel axis directed toward the main flow. Axial and radial distributions of the temperatures were measured in four channel cross sections above the jets injection point. An empirical dependence is proposed to calculate the axial depth of penetration the counter flow jet. The dependence generalizes the measurement results and is in agreement with the data of other authors. The relationship between the parameter of counter flow jet penetration depth and the parameter of impinging jets radial depth of penetration was revealed. Experimental data are in qualitative agreement with the numerical simulation results.


      PubDate: 2014-09-04T19:42:16Z
       
 
 
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